1. Chapter 18.1 Contributors of Genetic Diversity in Bacteria

2. Bacterial Genome Most bacteria contain double stranded, circular DNA Most bacteria reproduce asexually, making offspring identical to parent Mutations account for the slight differences in genetic make-up -probability of mutations can occur 1 in 10 million Diversity also arises from genetic recombination of DNA from two different sources

3. Gene transfer or Recombination Eukaryotes use meiosis and fertilization to bring DNA from two different organisms together Prokaryotes use 3 different processes: 1. Transformation 2. Transduction 3. Conjugation

4. Transformation uptake of naked or foreign DNA from the surrounding environment that alters cell’s genotype and phenotype - can change nonpathogenic bacteria into pathogenic form

5. Transduction Process where bacterial genes are randomly transferred form one cell to another *fragment of host cell DNA and viral DNA are integrated into another host cell’s replication, crossing over occurs and recombination takes place

6. Conjugation Direct transfer of genetic material between two bacterial cells temporarily joined One way transfer of DNA from donor male to recipient female Appendage know as sex pilus contacts recipient and retracts pulling two cells closer together- forms a mating bridge

7. Conjugation Conjugation results from the presence of special piece of DNA called an F factor (fertility) *can be present as segment of DNA or *Plasmid – small, circular self replicating DNA separate from chromosome - F plasmid consists of 25 genes and is required for production of sex pili * Hfr cell ( High frequency of recombination) – cell with F factor already built into the chromosome

8. F plasmid Conjugation

9. R Plasmids Some bacterial contain resistance genes that code for enzymes that destroy certain antibiotics – R plasmids (resistance) *most likely results from mutations R plasmids contain genes for sex pili for transfer of resistance from one cell to the next R plasmids can carry as many as ten genes for resistance to each type of antibiotic

10. Transposable Elements Genetic elements that cause DNA of a single cell to recombine by way of an intermediate - exist only in chromosomal or plasmid DNA Move DNA by cut and paste or copy and paste method- copies at original site, then copies inserts in other places *does not required complementary base pair for insertion (no homologous chromosome required)

11. Transposable Elements Insertion sequences- contain inverted repeats of DNA sequences that flank a transposase gene – moves sequences from one site to another within genome Transposons – longer more complex sequences that are transposed in genome to other locations *may help bacteria adapt to new environments

12. Chapter 18 Bacterial Regulation of Gene Expression

13. Response to Environment How can bacteria tune their metabolism to changing environments? Control occurs at 2 levels: 1. Cells can adjust activity of enzymes already present -sensitivity to chemical cues will increase or decrease activity (feedback inhibition) 2. Cells can adjust the amount made of certain enzymes -regulate expression of genes coding for enzymes

14. Operons Operator – segment of DNA positioned within or between promoter and enzyme coding genes that controls access to RNA polymerase Operon – cluster of genes with related functions ex: promoter, operator and genes they control for enzyme production

15. Operons Repressor- protein that reverses the action of operons - binds to operator and blocks attachment to RNA polymerase; prevents transcription of genes

16. Repressible and Inducible Operons Repressible operons – transcription is active but can be inhibited when a small molecule allosterically binds to protein EX: tryptophan to trp repressor Inducible operons – usually turned off but can be stimulated when a small molecule binds to regulatory protein EX: allolactose to lac repressor

17. Inducible Operons Absence of lactose vs. Presence of lactose

18. Positive Gene Regulation Occurs when a regulatory protein interacts directly with genome and switches transcription on. EX: CAP (catabolite activator protein) -activates transcription - on/off switch and volume control